Fine granulator



A ril 1, 1969 w. M. SHELDON 3,436,025 I FINE GRANULATOR Original FiledApril 29, 1963 INVENTOR. 4 WILLIAM M. S HELDDN' ATTORNEY Sheet of 5'April 1, 1969 w. M. SHELDON FINE GRANULATOR Original Filed April 29,1963 INVENTOR.

WILLIAM M. SHELDON ATTORNEY W. M. SHELDON FINE GRANULATOR A ril 1, 1969Sheet Original Filed April 29, 1963 INVENTOR.

' WILLIAM H. SHELDON ATTORNEY April 1, 1969 w. 9|. SHELDON FINEGRANULATOR Sheet 4 or 5 Original Filed April 29, 1963 INVEN TOR. WILLIAMH. SHELDON 7 zzvxw ATTORNEY A ril 1, 1969.

w. M. SHELDON. 3,436,025

FINE GRANULATOR Original Filed April 29, 1963 NVENTOR WILLIAM M SHELDONATTORNEY United States Patent U.S. 'Cl. 241-15 1 Claim ABSTRACT OF THEDISCLOSURE Method of comminuting material by subjecting materialconfined in suspended condition within a generally cylindricalcomminuting zone by a selectively directed flow of gaseous carrier tothe cutting impact of multiplicities of discrete rapidly moving acuteangle shearing edges disposed in selectively spaced relation to saidcomminuting zone and to each other to facilitate said selectivelydirected flow of gaseous carrier therepast.

This is a division of my copending application Ser. No. 276,645 filedApr. 29, 1963, now Patent No. 3,241,776.

This invention relates to the comminution of material and particularlyto an improved method for effecting comminution of suspended material bycutting impact on a shearing edge in the presence of a selectivelydirected gaseous carrier.

comminution of material by impact pulverization is widely employed inthe commercial arts and widely varying types of apparatus are utilizedin accord with the type of material to be comminuted and the desiredparticle size range of the resulting comminuted product. Comminutingapparatus of the so called hammer mill types are Widely used foreffecting impact pulverization of materials to a particle size range ofabout 5000 to 40 microns. Such hammer type mills are generallycharacterized by a high speed rotating shaft having mounted thereon aplurality of hammerlike members. Most, if not all, mills of this typeeffect reduction by impact, while the material is in suspension, inconjunction with an associated breaker surface usually constituted by apart of the housing surrounding the rotating elements. 'Such mills.however, are usually characterized by the production of what for manyend uses is an unacceptable amount of ultra fines and an undue amount ofheat generation. The development of such ultra fines is usuallyobjectionable as, for example, when the comminuted material is to beused in forming tablets or for injection molding. The development ofundue amounts of heat is particularly objectionable in the handling ofmaterials that tend to agglomerate, either by release of water ofcombination or hygroscopicity or by reason of sensitivity totemperature.

This latter problem has become of increasing importance with thecontinually expanding use of synthetic resins and so called plastics andother polymerization products, many of which are somewhat resilient innature and/or have a tendency to become soft and plastic beyond certaintemperatures. In the attempted handling of materials of the types abovenoted in conventional hammer mill type apparatus various expedients,such as the prereduction of product temperatures or of ambient airtemperature by the utilization of Dry Ice or other refrigerants havebeen employed to limit the degree of temperature rise and to limit themaximum temperatures attained during comminution. Such expedients,however, are palliative in nature at best and, apart from the additionalexpense involved, have been characterized with a marked lack ofcommercial utility due to necessarily reduced production,

3,436,025 Patented Apr. 1, 1969 increased cost and in some instances,the necessity of removing, by a subsequent drying operation, atmosphericmoisture condensation that becomes incorporated in the comminutedmaterial.

This invention may be briefly described as an improved method foreffecting comminution of suspended material by cutting impact withrapidly moving acute angle shearing edges in a rotor induced selectivelydirected gaseous carrier which conveys heat or other agglomerationinducing factors away from the locus of material deformation and servesto rapidly reduce the temperature of the comminuted product.

Among the advantages of the subject invention is the permittedcomminution, at ambient air temperatures and with a markedly decreasedtemperature rise, of an extended range of materials including many, ifnot most, of those whose comminution is effected only with difiiculty,if at all, in conventionally constructed impact pulverization apparatuseven with the expedients above noted. Other advantages of the subjectinvention include a marked increase in induced flow of gaseous carrierinto and through the locus of deformation, an improved control ofparticle size range of the resulting product and the avoidance of theproduction of undue amounts of ultrafines characteristic of impactpulverization operations. Still other advantages include the provisionof greatly extended effective length of cutting edge, markedly improvedyields per unit power input and a simplicity of construction thatpermits appreciable economies both in initial cost and maintenance ofapparatus embodying the subject invention.

The primary object of this invention is the provision of an improvedmethod for effecting comminution of suspended material by cutting impactwith a rapidly moving shearing edge in a rotor induced selectivelydirected gaseous carrier which serves to convey heat or otheragglomeration inducing factors away from the locus of materialdeformation and rapidly reduces the temperature of the comminutedmaterial.

Another object of this invention is the provision of improved method foreffecting comminution of agglomerative materials.

Other objects and advantages of the invention will be set forth in thefollowing specification and claims and will be ascertainable from theappended drawings which illustrate, by way of example, the principles ofthe invention as the same would be practiced in a presently preferredembodiment of a comminuting apparatus.

Referring to the drawings:

FIGURE 1A is an oblique view, partially broken away, of a mill (with thehousing cover removed) incorporating the principles of this invention;

FIGURES 1B and C are side elevational and plan views, respectively, ofthe mill illustrated in FIGURE 1A and with the housing cover in place;

FIGURE 2 is a schematic and somewhat idealized plan view of theessentials of the comminution chamber and rotor assembly containedtherein as the same would be viewed with the housing cover portionthereof removed;

FIGURE 3 is a sectional view taken on the line 33 of FIGURE 2;

FIGURE 4 is a side elevation, in enlarged scale, of a presentlypreferred configuration for a fan blade type spacer element;

FIGURE 5A is a schematic representation of an air injector type ofmaterial feed which may be utilized in conjunction with the subjectmill;

FIGURE 5B is an enlarged oblique view of a preferred configuration forthe saw teeth on the rotor assembly.

Referring to the drawings, there is provided a housing assembly,generally designated 1 and formed of a base member 4 and a substantiallysemi-cylindrically shaped upper or cover member 6 removably securablethereto. The base and cover members 4 and 6 are shaped to generallydefine an internally disposed comminution chamber 3, a material feedchannel communicating therewith and a dependent receiving chamber 7 forthe comminuted material after the same passes through thesemi-cylindrically shaped screen member 32 which also serves tocooperatively define the above mentioned comminution chamber 3. As bestillustrated in FIGURE 1B, the cover member 4 is provided with aplurality of particularly located circular air inlet apertures 16,suitably three, in each of the side wall portions 26, 28 thereof, aswell as a material entry aperture 8 in alignment with the feed channel 5to accommodate material entry into the comminution chamber 3 by a wormtype feed mechanism generally designated 10. The air inlet apertures 16are preferably screened with a coarse screen or mesh of suitable size asto prevent egress of uncomminuted material there through but yet notimpede air flow therethrough into the comminution chamber.

The base housing member 4 is suitably shaped to terminally support theextending arms 12 of a pair of suspended rotor supporting journals orbearing assemblies 14. A rotor shaft 22 is rotationally suported in thejournals 14 and is provided with an extension end 24 extending beyondone side of the housing for facilitating a drive connection thereto. Asbest shown in FIGURES 2 and 3, the internally disposed comminutionchamber 3 is essentially of cylindrical configuration being defined bythe apertured and essentially planar -wall portions 26, 28, an uppercurved wall 30 of essentially semi-cylindrical configuration and a lowercurved wall formed by the perforate and removable plate or screen 32 ofcomplemental semi-cylindrical configuration. As will be apparent tothose skilled in this art, the removable lower screen 32 is providedwith apertures of predetermined size to determine the maximum particlesize of the comminuted material that is permitted to exit from thecomminution chamber.

Disposed within the comminution chamber 3 is a rotor assembly formed ofa plurality of circular saw-like blades or serrated periphery disc-likemembers 34 fixedly mounted on said rotor shaft 22 and maintained inclose parallel spaced relation by interposed spacer washers 36. Asillustrated in FIGURES 1A, 2 and 3, the disc-like members 34 areperipherally saw toothed so as to present a succession of cutting edgesin the direction of rotation and, for most applications are preferablycollectively mounted in a slightly skewed or offset relation asindicated by the angle A (FIGURE 2) to a plane normal to the axis ofrotation of the shaft 22 to minimize, if not prevent, undesired trackingof material introduced through the feed channel 5. As best illustratedin FIGURE 5B the saw teeth on the periphery of the blade members 34 arepreferably shaped to provide a chisel-like, acute angle cutting edge 35disposed substantially parallel to the axis of the rotor shaft 22. Asillustrated, the trailing edge of each tooth declines so as tocompletely expose the cutting edge on the succeeding tooth. Theprovision of the above described chisel-like cutting edge disposedsubstantially parallel to the rotor shaft axis results, when the numberof available teeth per blade and number of blades are considered, in agreatly increased effective length of cuttting edge all localized withinand operatively displaceable through the locus of material deformation.Secured to the undersurface of the upper curved wall 30 and disposedremote from the material feed aperture 8 is a deflector type linermember 31 having a surface configuration disposed in facing relationwith the rotor periphery and of suitable contour to deflect material ina more or less radial direction back into contact with the cutting edgedperiphery of the saw toothed rotor.

As will be apparent from the foregoing, the saw tooth configuration ofthe periphery of the disc or blade members provides a plurality ofsuccessive selectively positioned cutting edges, which, upon engagementwith the mate- 4 rial, effect comminution primarily by a cutting impactwith a rapidly moving chisel-shaped shearing edge, as distinguished fromthe so-called pure impact principle of grinding or comminution.

Referring again to FIGURES 2 and 3, each of the saw blade members 34 isprovided with a plurality of apertures 38, suitably four in number,preferably arranged in equiangular relation and disposed substantiallytangent to the periphery of the interposed spacer element 36 and insubstantial radial alignment with the screened air inlet apertures 16disposed in the opposite side wall portions of the cover member 6.Although discrete circular air inlet apertures 16 are preferred, asingle elongate arcuate aperture in each side wall subtending an arc ofabout degrees would also be suitable. As illustrated, the blade members34 are mounted on the rot-or shaft 22 in such manner as to preferablydispose the blade apertures 38 in substantially axial longitudinalalignment. In the specifically illustrated embodiment wherein ambientair inlet apertures 16 to the comminution chamber are disposed on bothside walls of the cover member 6, a balanced bidirectional air flowtoward the center of the rotor is obtainable by preferential utilizationof an unapertured or imperforate central blade member 34a and bybeveling or tapering the apertures in the blades on either side thereofso as to be divergent in the direction of the desired air flow, as bestshown in FIGURE 2. The inclusion of the beveled or tapered apertures 38in the saw blade members 34 and the alignment thereof in the mannerdescribed thus provides a plurality of channels for selectively directedgas flow, specifically a fiow of ambient air, longitudinally of therotor 22. In addition thereto, the interposition of the spacer members36 intermediate adjacent blade members serves to separate the same andthereby define a plurality of radially disposed channels for selectivelydirected gas flow, each having a plurality of common junctions with theaforedescribed longitudinal channels.

It is to be understood that while the presently preferred embodiment isconstructed as above set forth, a balanced bidirectional gas flow willalso be obtained by utilization of an apertured but preferably unbeveledcentral blade 34a. Also, as now will be apparent to those skilled inthis art, other arrangements as to degree or selective direction ofbevel, and size and location of the saw blade apertures may be made asdesired to obtain optimum results with a particular machine and/orparticular material to be comrninuted, for example, unbeveled apertures38 in association with interposed spacer washers 36 of the fan bladetype configuration, as illustrated in FIGURE 4, will also result in thedesired and selectively axially directed flow of the gaseous carrier. Inaddition thereto, other expedients, such as an injector type materialfeed, as illustrated in FIGURE 5A may be employed.

In operation of the subject unit, unidirectional high speed rotation ofthe rotor assemlbly effects a positively induced and greatly increasedprimary bidirectional flow of ambient air or other gaseous carrier intothe comminution chamber through the ambient air inlet apertures 16 oneach side of the housing, longitudinally of the rotor shaft 22 throughthe tapered or beveled apertures 38 therein and, intermediate each pairof blades 34, a secondary flow radially outward into and through thelocus of comminution, such radial flow being accelerated and reinforcedby the action of the fan type spacer members 36 when the same areemployed as heretofore described.

Although the mechanics of the above described rotor induced air flowpattern are not fully understood at the present time, it is believedthat it serves, in addition to maintaining the material to be comminutedin suspended and separated condition in the vicinity of the chiselshapedblade cutting edges, to uniformly convey heat away from the locus ofdeformation and to markedly and rapidly reduce the temperature of thecornminuted product prior to the necessary intersurface contact thereofrequired for agglomeration.

The effect of maintaining the material to be comminuted in suspended andseparated condition and uniformly conveying heat away from the locus ofdeformation has resulted, as shown in tests, with a saw tooth rotorembodying this invention, in the (1) production of granutained ascreened product analysing 100%, -40 mesh and 20%, l40 mesh whengrinding the resin with an anti-calcing agent and 100%, -40 mesh and11.1% -140 mesh when no anti-caking agent was added. The temperature ofthe ground material never exceeded 98 F. with lar grinds with a minimumof ultra-fines, (2) marked 5 a 75 F. feed material and 80 F. atmospherictemperaincrease in the production rate per H.P./-hr., (3) cornture.minution, at satisfactory commercial rates, of many In general, andapart from the specific advantages dematerials heretofore reduceableonly at reduced rates lineated above, tests to date indicate that unitsincorporatand/ or with the expedients referred to earlier in conveningthe subject invention produce satisfactory results in tional equipment,(4) reduction in grind temperatures, about 80% of those cases 'whereinit has been tested on (5) avoidance of the need, in many case-s, of theexpedimaterials which could not be satisfactorily processed by entsreferred to earlier. conventional equipment. Also, tests have shown thatit is By way of example, in a recent comparative test on generallypossible to operate the subject unit at apprecipolystyrene having DryIce necessarily mixed herewith, a ably higher mill temperatures than canbe tolerated with conventional machine incorporating a standard stirrulpconventional pulverizing machines. For examlple, it has type rotorproduced 33 lbs. per hour of comminuted prodbeen found possible withapplicants device to process net at 3 and /2 HP. A saw tooth rotor unitemlbodying low density polyethylene at outlet temperatures as high theprinciples of the subject invention operating on the as 200 F. withoutany fusing in the comminution chamsame material produced an equivalentcomminuted prodher. Nitrol rubber has been successfully run withoutfusuct at a rate of 60 lbs. per hour at 1 HP. Other comparaing at outlettemperatures of 160 F. This feature is of tive tests on varyingmaterials have shown as much as extreme importance in increasingcapacity and reducing a 4 to 1 capacity ratio in favor of the subjectinvention the size of required equipment to do a particular job. overconventional and commercially available equipment. It is also indicativeof the fact that something more than In another comparative test oncellulose propionate (a a simple reduction of heat rise is responsiblefor the unfibrous material similar to cellulose acetate), aconvenexpected beneficial and new results that have been obtionalmachine with a bar hammer rotor produced 12.5 tained from the subjectconstruction to date. lbs. per H.P. hour of 92.6% through mesh productIn addition to the above mentioned comparative test with a .039 Rd. Pt.screen. The production obtained by results, the subject invention hasbeen found to be particuthe unit embodying the subject invention andwith an 0 larly advantageous in the production of high densityequivalent speed and screen, was 20 lbs. per H.P. hour powdered sugar(47 /2 lbs. per cubic foot packed density) and of an average analysis of94% through a 40 mesh and and which after comminution has beenremarkably free with a grind temperature about 25 F. lower than thatfrom lumping, even though no starch was added before produced in theconventional machine. g-rindinlg. Tests have been run on lots of sugarsfrom dlif- In still another comparative test, pure gum nitrol rub- 35ferent refiners, and comminution has been performed unber (Hycar) couldnot be satisfactorily comminuted a der a wide range [of relativehumidities with no apparent conventional bar hammer rotor machine due toa rapid difference in the non lump-ing storage characteristics. rise ntemperature, softening of the material in the Applicant is unable toexplain this highly advantageous gmlldlflg chamber and smoking of thematerial. The same result except to suggest that it may the due to thecommaterial was processed satisfactorily in a unit embodying b'inedfeatures of maintaining the material to be cornthe subject inventionwith and Rd. Pt. screens minuted in suspended condition and uniformlypassing at respective capacities of 18.5 and 27 lbs. per H.P. hour. airthrough the suspended material while it is being com- In other tests ona polyester resin having a. melting minuted, combined possibly with theadditional fact that point of 235 F. and a softening point of between F.the material is being comminuted by a fast acting shearing and F. anunsuccessful attempt was made to pro- 45 action, on an acute anglecutting edge. duce a screened product of 100%, -40 mesh and 15% Thefollowing is a list of random test results on maximum, -140 mesh usingliquid CO as a coolant, on various materials which to date have beenfound to be a bar type conventional machine. Using applicants deviceparticularly adapted to comminution by method incoron the same materialand without coolant there was obporatin g the subject invention:

Material Character Mill temp. Lbs. per Grind F.) hr. Cellulosepropionate Fitbroug and moderately 148 19. 0 9475-40 Cocoanut, strippedBrii t fia; 19%+14 Cofiee, roasted do 23%40 Licorice extract Verybrittle 300 2%+14 PVC, chlorinated type No.1 Tough 140 7.5 al a-1i?)Polyester, pigmented resin -do 146 3. 3 i /Elli Polyethylene, RD. andcarbon black do 7. 5 Polyethylene and plgment Fine, granular with 2%% 84200 Polyethylene, L.D. reactor flake rgiiiiii i j 200 8 %40 Polystyrenedo 105 90 1. 3%+12 Polystyrene, pigmented, 50:50 TiOz... Brittle 120 5.5 $133 Potatoes, dried sliced, raw Hard 200 g Resin, misc. A.C.XModerately tough 120 22.0 3;;128 Rice Hard 210 oiiI-i 49%10+50 Rubber,nitrol (crude) type No. 1 Tough resilient 4 oiiiglliii Rubber, nitrol(crude) type No. 2 do 18 51%-50 See footnote at end of table.

Material Character Mill temp. Lbs. per Grind C F.) hr.

Rubber, silicone flashings (cured) Tough 15 4. %+20 82%20+50 SugarBrittle 104 190 99. 8%70 88. 3%200 Teflon and fibre glass 70:30 nu'xSoft fibrous lumps 60 Vinyl scrap Tough 194 12 1%+12 2%100 Wheat Hard450 7%8 1 Excellent color dispersion.

Other materials which have also been found to be particularly suited forcornminution by method incorporating the subject invention include:

elastorners leather scraps nylon pellets polyurethane scrap rubbersynthetic crude rubber vinyl resins.

Having thus described my invention, I claim:

1. In the comminution of material, the steps of confining suspendedmaterial to be comrninuted within a comminuting zone of generally hollowcylindrical configuration by a selectively directed flow of gaseouscarrier and subjecting said suspended material to the cutting impact ofmultiplicities of discrete rapidly moving forwardly directed acute angleshearing edges disposed in substantially parallel relation to the axisof said comminuting zone and in spaced relation therealong and which arerapidly moving in a circular path of travel through said comrninutingzone, said selectively directed flow of gaseous carrier including afirst component substantially parallel to the axis of rotation of saidshearing edges and intermediate said axis of rotation and the path of 15travel of said shearing edges and a second component substantiallyperpendicular to the axis of rotation of said shearing edges and flowingintermediate the same.

References Cited UNITED STATES PATENTS 2,219,720 10/1940 Clark et al241- 55 X 2,939,638 6/1960 Haigh et al. 24l55 X 3,123,312 3/1964 Palyi24l55 2,726,045 12/ 1955 Hinerfeld 241-16 2,941,731 6/1960 Lykken 24l182,974,883 3/1961 Engel 241-17 FOREIGN PATENTS 655,892 1/ 1938 Germany.

JAMES M. MEISTER, Primary Examiner.

US. Cl. X.R. 24l27,

